Page 96 - THE PERCEPT STUDY Illness Perceptions in Physiotherapy Edwin de Raaij

Chapter 5
Control, Treatment Control, Identity, Concern, Coherence, and Emotional Response. The IP dimensions of Control beliefs (Personal/Treatment) and Coherence were converted before statistical analyses as they are scored in reverse. Higher scores on Brief IPQ-DLV were theo- rized to have a greater chance on poor recovery. The ninth IP question, the Causal dimension, has rank-ordered free-text responses and was not added as a predictor.
Dependent variables:
For Global Perceived Effect (GPE), we used a 7-point scale ranging from ‘completely recovered’ to ‘very much worsened’. The GPE is a reliable measurement 22 with a clinically-meaningful improvement cut-off point at ≤ 2 on a 7-point scale 23.
We defined the depended variable poor recovery in three different ways 24;
• pain intensity at follow-up; score of ≥ 3 on an 11-point NRS (0-10)
• physical function (PF) at follow-up; score of ≥ 3 on an 11-point NRS (0-10)
• Global Perceived Effect; score of ≥ 3 on 7-point GPE ordinal scale
Statistics
In addition to age and gender, baseline scores were assessed for PI, PSFS, pain duration, number of pain sites, the 4DSQ, and the Brief IPQ-DLV, as percentages or means (standard deviation (SD)).
Hierarchical logistic regression models were constructed to examine the added predictive value of baseline ‘poor recovery’ (at 3 months). In the first block, age, gender and baseline scores for generic prognostic factors (psychological measures, PI, limitations in PF, number of pain sites and duration of pain) were entered as fixed (independent) variables. In the second block, baseline IPs with univariate significant ORs (p < 0.10) were added to the model. The final model was obtained by using the backward stepwise method. The goodness-of-fit of the model was described by the Nagelkerke R2 and the Receiver Operating Characteristics (ROC) curve with Area Under the Curve (AUC). Goodness-of-fit of the AUC was judged thus: 0.90 - 1.0 Excellent; 0.80- 0.89 Good; 0.70- 0.79 Fair; 0.60- 0.69 Poor; 0.50- 0.59 Fail. For calibra- tion, we checked the goodness-of-fit using the Hosmer & Lemeshow test (p < 0.05). The SPSS package 25TM was used to analyze the data.
For our research question ‘Is there an association between the 4DSQ and the Brief IPQ- DLV?’, we used the non-parametric Spearman’s rank correlation coefficient. To interpret the strength of the correlation, we used the following classification; 0.00-0.10 negligible, 0.10- 0.39 weak, 0.40-0.69 moderate, 0.70-0.89 strong and 0.90-1.00 very strong 32.
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